Move src/MaxText/layers to src/maxtext/layers

[dipannita08]

Description

Move src/MaxText/layers to src/maxtext/layers.

Tests

• Unit tests
• Github CI

Please describe how you tested this change, and include any instructions and/or
commands to reproduce.

Checklist

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[codecov]

Codecov Report

❌ Patch coverage is 96.06742% with 7 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/maxtext/layers/encoders.py	33.33%	4 Missing ⚠️
src/MaxText/integration/tunix/tunix_adapter.py	0.00%	1 Missing ⚠️
src/MaxText/layerwise_quantization.py	0.00%	1 Missing ⚠️
src/MaxText/utils/ckpt_conversion/to_maxtext.py	0.00%	1 Missing ⚠️

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[SurbhiJainUSC]

This needs to be moved to src/maxtext/models along with other models modules: https://screenshot.googleplex.com/tq9zWqrLQ7ASYhE